• Journal of Environmental Science International
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• v.15 no.6
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• pp.579-586
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• 2006

The purposes of this paper were to monitor the temperature rising courses and spark discharge of the modified granular activated carbon (GAC) by microwave (MW) irradiation and to evaluate absorption of benzene. The GAC coated on $SiO_2$, boron, talc, ferrite was named as the modified GAC. Thermal and spark discharge measurement of virgin GAC and modifed GAC has been carried out using a MW device operating at 2450 MHz under various energy conditions. The results of this paper as follows. First, the modified GAC is more efficient than the virgin GAC in temperature control. Temperature gradient of the modified GAC is more lower than that of virgin GAC. The temperature gradient of GAC was observed in the following order : virgin GAC, Mn-Zn ferrite/GAC, Ni-Zn ferrite,/GAC, $SiO_2/GAC$, Boron/GAC, Talc/GAC. Second, the spark discharge of the modified GAC was diminished, compared with that of virgin GAC. Because of its excellent electrical insulating properties, the coating material prevents the spark discharge. Finally, the benzene adsorption capacity of the modified GAC decreased due to diminishing of adsorption site by the coating material. Considering the temperature gradient and spark discharge of GAC, the GAC coated $SiO_2$ would be appropriate absorbent under irradiation of MW.

• Journal of the Korea Convergence Society
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• v.11 no.10
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• pp.63-69
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• 2020

In this paper, a small microwave sensor that can be applied to a wearable device is proposed because it can detect the heartbeat signal of a human body moving irregularly at low speed. It consist of balanced microstrip radiation patches in the 2.4 GHz ISM band, self-oscillation detection circuit, and feedback circuit. Based on the theoretical development and simulation, the validity of the proposed structure was confirmed and the manufactured prototype was tested. The board size of the circuit is as small as 65mm × 85㎟, and has a low power consumption of 60mW thanks to the simple RF circuit structure. Finally heartbeat signal has been obtained from a human body moving at low speed (0.5Hz) within a linear distance of 2 to 30mm close to the sensor and a lateral distance of ±20mm.

• Journal of Biosystems Engineering
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• v.39 no.4
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• pp.304-309
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• 2014

Purpose: Weeds cause significant losses in agricultural production. In this study, we investigated the effect of microwaves on the germination rates of cress and arugula seeds to determine whether microwaves could be developed as an effective alternative to conventional chemical-based herbicides. Methods: Seeds were planted at equal depths (8-10 mm) in a soil-turf mixture, and seeds were exposed to microwaves for 126 s, 70 s, and 50 s in a device constructed specifically for this study. A microwave tunnel was built using a variable speed conveyor belt and 4 magnetrons with a combined output power of 2.8 kW. Seeds that were not exposed to microwaves were germinated with regulated irrigation, temperature, and humidity controls in parallel with the treated seeds, and the germination rates were compared among the treatment groups. Results: We found that the exposure of cress and arugula seeds to microwaves for 126 s inhibited germination close to 100%. Cress seeds treated with microwaves for 50 s showed 95% germination compared to 65% germination of the untreated cress seeds. Conclusions: We predict that the thermal effect of microwave energy affects the germination ratio and germination rate of seeds.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.2
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• pp.151-158
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• 2002

In this paper, Phase locked microwave oscillator having the low phase noise and high stability for digital MMDS down converter was designed. we have been analyzed the low phase noise properties by the active device nonlinear equivalent circuits and derived the necessary and sufficient conditions for high stable voltage control oscillator. And it is applied to phase locked loop, we design the phase locked microwave oscillator of frequency synthesizer. Experimental results of designed phase locked oscillator shows -85dBc/Hz @ 10KHz phase noise properties and simulation result is -90Bc/Hz @ 10kHz respectively we shows that proposed low phase noise and stable conditions of phase locked microwave oscillator can be applied to design the high stable digital MMDS frequency synthesizer.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.287-290
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• 2003

For microwave device applications, c-axis oriented high temperature superconducting YBa$_2$Cu$_3$O$_{7-{\delta}}$ (HTS-YBCO) epitaxial thin films on the r-cut sapphire substrate(Al$_2$O$_3$) were prepared. In order to reduce the lattice mismatch with a substrate and to enhance the crystallity of HTS thin films, CeO$_2$ buffer layer on the r-cut sapphire substrate was grown by the RF-magnetron sputtering. The YBCO films on the CeO$_2$ buffer layer were deposited using the pulsed-laser deposition (PLD) method. These HTS YBCO /CeO$_2$/Al$_2$O$_3$ multilayer thin films(30 $\times$ 30 mm$^2$) routinely exhibited a critical temperature(T$_{c}$) of 89 K from the R-T measurement. Using HTS YBCO/CeO$_2$ /Al$_2$O$_3$ multilayer thin film. We fabricated and characterized the microwave passive devices (planar type filters) with cryopack-age such as the coupled -line type low-pass filter (LPF) and the open-loop meander type bandpass filter (BPF).filter (BPF).).

• Atmosphere
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• v.32 no.4
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• pp.263-276
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• 2022

The observation error of satellite radiation data that assimilated into the Korean Integrated Model (KIM) was diagnosed by applying the Hollingsworth and Lönnberg and Desrozier techniques commonly used. The magnitude and correlation of the observation error, and the degree of contribution for the satellite radiance data were calculated. The observation errors of the similar device, such as Advanced Technology Microwave Sounder (ATMS) and Advanced Microwave Sounding Unit-A shows different characteristics. The model resolution accounts for only 1% of the observation error, and seasonal variation is not significant factor, either. The observation error used in the KIM is amplified by 3-8 times compared to the diagnosed value or standard deviation of first-guess departures. The new inflation value was calculated based on the correlation between channels and the ratio of background error and observation error. As a result of performing the model sensitivity evaluation by applying the newly inflated observation error of ATMS, the error of temperature and water vapor analysis field were decreased. And temperature and water vapor forecast field have been significantly improved, so the accuracy of precipitation prediction has also been increased by 1.7% on average in Asia especially.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.26-30
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• 1995

We describe the preparation and characterization of epitaxial thin films made with high temperature superconductor, $YBa_2Cu_3O_{7-\delta}$. The influence of processing parameters for YBCO thin films on MgO substrates in-situ grown by the pulsed laser deposition, including parameters of a laser beam energy, oxygen pressure, substrate temperature, target-substrate dis-tance is discussed. The characteristics of YBCO thin films were analyzed by using XRD, R-T measurement, AFM, crosssectional TEM, and RBS. For examples of microwave device applications, The fabrication and characterization of the microstrip lowpass filter and bandpass filter are also presented.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.9
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• pp.1727-1732
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• 2011

In order to realize a high performance(low loss, high isolation) microwave power divider/combiner, we have designed the power combiner/divider precisely in accordance with the different hight of central part. In the case of the high central part of the hight of $h_r$=10.2, a compensating part of the conical line is inserted in the conical conversion transmission line, and in the case of low central part of the hight of $h_r$=5.0, the conical conversion transmission line is remodeled into the 2-stage bend structure. In both case, the reflection characteristics are improved to 30dB over the operating frequency range of 5GHz bandwidth. A resistance is inserted between the peripheral ports so as to try to improve the isolation characteristics of the device. For the 16-divider/combiner, the isolation characteristics are improved to 10dB over the operating frequency range of 5GHz bandwidth.

• JSTS:Journal of Semiconductor Technology and Science
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• v.6 no.3
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• pp.182-188
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• 2006

An artificial neural network model for the microwave characteristics of an InGaAs/InP hemt for 70 nm gate length has been developed. The small-signal microwave parameters have been evaluated to determine the transconductance and drain-conductance. We have further investigated the frequency characteristics of the device. The neural network training have been done using the three layer architecture using Levenberg-Marqaurdt Backpropagation algorithm. The results have been compared with the experimental data, which shows a close agreement and the validity of our proposed model.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.222.1-222.1
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• 2014

Flexible device 및 OLED 디스플레이 제조를 위한 산화물 반도체 보호막 증착 및 encapsulation 공정을 위해 균일한 대면적 플라즈마를 만들기 위한 다양한 연구가 진행되고 있다. 초고주파 플라즈마는 고밀도, 고효율의 플라즈마를 저진공에서 쉽게 생성시킬 수 있고 다양한 전력결합방법을 통해 대면적 확장성이 우수한 장점이 있다. 본 연구에서는 TEM 웨이브가이드로 파워가 전달되는 선형 초고주파 플라즈마 소스에 대한 2차원축대칭 유체 시뮬레이션을 수행하였다. Ar 가스 압력과 초고주파 입력전력이 증가함에 따라 전자밀도가 증가하였고 도파관 방향으로 플라즈마의 길이가 증가함이 관측되었다. Quartz Tube 표면 가까이에서 전자밀도가 가장 높게 나타났다. 전자의 에너지 손실 채널중 가장 많은 부분을 차지하는 것은 여기종 생성에 따른 에너지 손실이었으며 탄성 충돌에 의한 에너지 손실이 두 번째로 큰 부분을 차지하였다.